.container {
  width: 400px;
  height: 400px;
  display: flex;
  flex-wrap: wrap;
  div {
    flex-basis: 33.33%;
    border: 1px solid #ececec;
    box-sizing: border-box;
    cursor: default;
    color: #fff;
  }
  div.isActive {
    background-color: pink;
  }
  div.click {
    position: relative;
    border: 1px solid #2b92d4;
    border-radius: 5px;
    color: #fff;
    font-size: 20px;
    text-align: center;
    cursor: pointer;
    box-shadow: 0 1px 2px rgba(0, 0, 0, .3);
    overflow: hidden;
    background-image: linear-gradient(#6cc3fe, #21a1d0);
    /*动画运动的数学函数：慢-快-慢*/
    -webkit-animation-timing-function: ease-in-out;
    /*动画名*/
    -webkit-animation-name: breathe;
    /*动画完成一个周期的时间*/
    -webkit-animation-duration: 2700ms;
    /*动画播放次数-永远*/
    -webkit-animation-iteration-count: infinite;
    /*动画是否循环交替反向播放-奇数次正向、偶数反向*/
    -webkit-animation-direction: alternate;
    animation: ease-in-out breathe 2700ms infinite alternate;
  }
  div.click:hover {
    background-color: darkred;
    color: #fff;
  }
}

@keyframes breathe {
  0% {
    opacity: 0.2;
    box-shadow: 0 1px 2px rgba(255, 255, 255, 0.1);
  }
  100% {
    opacity: 1;
    border: 1px solid rgba(59, 235, 235, 1);
    box-shadow: 0 1px 30px rgba(59, 255, 255, 1);
  }
}
